In the formulation of carriers for topical administration of therapeutic agents and other active ingredients, a wide variety of formulation components are employed, which are in many cases specifically adapted to the particular active ingredient to be applied.
A significant problem in the topical administration of many active ingredient compositions is that they are highly volatile in character. In consequence, evaporative losses of solvents from the active ingredient compositions are significant, and result in diminution of the treatment efficacy of such ingredient compositions. Evaporative loss of solvents from the active ingredient compositions therefore may severely diminish the therapeutic effect and/or duration of benefit of the active ingredient on the areas of the body to which the formulation has been topically applied.
As a result, increased amounts of the topical composition may need to be applied, to ensure the beneficial effect. This may in turn lead to gross overuse of the composition, in an effort to provide surplus material to compensate for evaporative losses from the active ingredient composition.
Another problem that frequently occurs in use of topical compositions, e.g., skin treatments, hair treatments, hair growth compositions, cuticle treatments, and the like, is that the active ingredient may be highly susceptible to systemic migration. By systemic migration is meant that the active topical agent penetrates through the skin, hair, nails, etc. into the system of the user, with consequent loss of surface activity of the active ingredient(s). As in the case of evaporative loss, systemic migration diminishes the beneficial effect of the active ingredient, with the same consequences as those discussed above in respect of evaporative loss of solvents.
Additionally, such systemic migration may result in systemic toxicity effects deriving from the active ingredient(s) intended to remain on the surface of the skin, scalp, hair, etc., which nonetheless pass into the body through the skin, hair follicles, and/or other systemic portals, to internal locales in the user's body where the active ingredient is not desired and where it may in fact contribute to adverse physiological side-effects. For example, a substantial proportion of daily users of commercially available 5% minoxidil formulations report incidences of heart palpitations 10-30 minutes after use and scalp irritation 1-2 hours after use.
There is therefore a continuing effort in the field of topical compositions containing active ingredients susceptible to such deficiencies, to develop improved compositions that retard evaporative loss of solvents from the formulation and that minimize systemic penetration of active ingredients.